Unraveling the vector nature of generalized space-fractional Bessel beams

We introduce an exact analytical solution of the homogeneous space-fractional Helmholtz equation in cylindrical coordinates. This solution, called the vector space-fractional Bessel beam (SFBB), has been established from the Lorenz gauge condition and Hertz vector transformations. We perform scalar and vector wave analysis focusing on electromagnetics applications, especially in cases where the dimensions of the beam are comparable to its wavelength (k(r) approximate to k). The propagation characteristics such as the diffraction and self-healing properties have been explored with particular emphasis on the polarization states and transverse propagation modes. Due to continuous order orbital angular momentum dependence, this beam can serve as a bridge between the ordinary integer Bessel beam and the fractional Bessel beam and, thus, can be considered as a generalized solution of the space-fractional wave equation that is applicable in both integer and fractional dimensional spaces. The proposed SFBBs provide better control over the beam characteristics and can be readily generated using digital micromirror devices, spatial light modulators, metasurfaces, or spiral phase plates. Our findings offer insights on electromagnetic wave propagation, thus paving a route towards applications in optical tweezers, refractive index sensing, optical trapping, and optical communications.

Automated summary

The exact analytical solution of the homogeneous space-fractional Helmholtz equation in cylindrical coordinates, known as the vector space-fractional Bessel beam (SFBB), has been introduced in this study. Scalar and vector wave analysis focused on electromagnetics applications, particularly in cases where beam dimensions are comparable to wavelength. The SFBBs, with continuous order orbital angular momentum dependence, serve as a bridge between ordinary integer Bessel beams and fractional Bessel beams, providing better control over beam characteristics and applications in optical devices.